Process for making crosslinked cellulose derivatives utilizing halo-acrylic acids



United States Patent PROCESS FOR MAKING CROSSLINKED CELLU- LOSEDERIVATIVES UTILIZING HALO-ACRYL- IC ACIDS Austin L. Bullock, Charles H.Mack, and John D. Guthrie, New Orleans, La., assignors to the UnitedStates of America as represented by the Secretary of Agriculture NoDrawing. Filed Jan. 17, 1964, Ser. No. 338,533

5 Claims. (Cl. 260-212) A non-exclusive, irrevocable, royalty-freelicense in the invention herein described, throughout the world for allpurposes of the United States Government, with the power to grantsublicenses (for such purposes, is hereby granted to the Government ofthe United States of America.

This invention relates to crosslinked fibrous cellulose derivativescontaining free reactive carboxyl groups, and to a process for producingsame.

-It is Well known that highly substituted cellulose derivativescontaining su'bstituents having hydrophilic groups such ascarboxymethylcellulose tend to swell, gelatinize, or even dissolve ineither dilute acids, dilute alkalies, or water. This tendency to swell,gelatinize, or dissolve when highly substituted prevents the use of suchderivatives in many cases where insolubility and a low degree ofswelling are important.

:It is also well known that crosslinking is closely related to the setthat is imparted to cotton cellulose either in the attainment ofresiliency and permanent creases in washwear fabrics or in thedevelopment of a fiber or yarn crimp needed to produce stretch yarns andfabrics. The presence of hydrophylic groups also have a pronouncedeffect on the properties.

While crosslinking is accomplished by reacting cellulose with di-haloand di-vinyl derivatives there have been no reports of the reaction ofvinyl halides with cellulose to form either a chemically modifiedcellulose or a crosslinked cellulose.

We have discovered that cellulose can be crosslinked by means ofhalo-acrylic acids, such as chloroacrylic acid. These cellulosederivatives, which contain both crosslinks between cellulose chains andfree, reactive carboxyl groups may be highly substituted, and at thesame time may be insoluble and highly resistant to swelling. in additionthese derivatives possess improved wrinkle resistant properties, andincreased water of imbibition, which is an indication of increasedmoisture absorptivity.

These derivatives can be prepared from either granular or fibrouscellulose; from yarns or from fabrics. The cellulose may be obtainedfrom wood pulp, cotton, hemp, ramie, or it may be a regeneratedcellulose, such as rayon. The cellulose derivatives provide an improvedabsorbent material, as well as an ion exchange material of value inbiochemical separations and other chemical processes. The derivativeswhen produced in the yarn form or in the fabric form provide usefultextile materials which have an enhanced afiinity for basic dyes. Thetabrics also possess improved wrinkle resistant properties.

The said cellulosic derivatives, object of this invention, may beprepared by reacting cellulose with a halo-acrylic acid such asalpha-chloroacrylic acid, beta-chloroacrylic acid,alpha-beta-dichloroacrylic acid, and the alkali metal salts of theseacids, in the presence of sodium hydroxide. The best results areobtained when an excess of the alkali is used. The pure acid, if liquid,can be used, or it can be diluted with a suitable solvent, such as wateror acetone.

The preferred concentration of the sodium hydroxide is an aqueous 20% to40%; however, the concentration of the sodium hydroxide may vary widelyso long as it is present in excess of the amount necessary to neutralize3,294,780 Patented Dec. '27, 1966 "ice any acidic materials developedduring the reaction. The sodium hydroxide may be applied to thecellulosic material either prior to the acid, or simultaneously with thesalt of the acid, or after the cellulosic material has been impregnatedwith the acid. When the cellulosic material is being impregnated ineither the yarn or the fabric form the process is carried out instandard padding equipment. The reaction in such cases is completed bycuring the textile material at temperatures about from to -120 C. Theextent of the reaction is limited at temperatures lower than about 80C., and excessive yellowing occurs at temperatures higher than about 120" C. In those instances where the alkali metal salts of thehaloacrylic acids are employed, we prefer to cure at temperatures offrom C. to 120 C. for periods of from 10 to 30 minutes, the lowertemperatures being used with the longer time intervals. In thoseinstances where the free haloacrylic acids are employed, we prefer tocure at temperatures of from C. to C. for periods of from 15 to 30minutes, the lower temperatures being used with the 10m er timeintervals.

If the pure acid in a concentrated solution of the acid is used forimpregnation the heat of neutralization and/ or reaction may besufiicient to complete the reaction. However, if either the salt alone,or the acid and the sodium hydroxide mixedprior to impregnation, areused for impregnation, curing at the higher temperatures is necessary.Once the reaction is complete the cellulosic material is washed untilfree of alkali, and dried in any feasible manner.

Proof of crosslinkage is established by submitting the cellulosicderivative to wetting with cupriethylenediamine hydroxide solution. Thelatter swells and dissolves cellulose, but does not afiect crosslinkedcelluloses. The presence of available carboxylic acid sites is indicatedby the affinity of the cellulosic materials for dyes such as methyleneblue. This is confirmed by titration of the cellulosic derivative with astandardized base solution.

-Prior to titration the material is, treated with dilute hydrochloricacid to convert the carboxylic acid groups from the basic to the acidicform. The cellulosic derivative is then washed with water, to eliminatethe ionic chlorine.

Resiliency of these derivatives is established by employing the WrinkleRecovery Test (ASTM Dl295-60T) values obtained upon testing the fabricsas the criteria. Absorbency of these derivatives is established by usingthe water of imbibition values as the, criterion. An increase in thevalue of the imbibitioncom-pa-red with the untreated cellulosicmaterialindicates increased absorbency in the treated cellulosicderivative.

The following examples are illustrative of the invention, and show partsand percentages by weight, unless otherwise stated.

Example 1 A sample of cotton printcloth was padded with a solutioncontaining 10 parts by weight of the potassium salt ofaIpha-chlo-roacrylic acid, 20 parts by weight of sodium hydroxide, and70 parts by Weight of water. The wet sample was placed on a pinframe,and dried and cured 10 minutes at 100 C.

The sample was then Washed, while still on the pinframe, with runningtap water until free of caustic, and dried on the pinframe. The productwas insoluble in a 0.5 molar aqueous cupriethylenediamine hydroxidesolution, and had a carboxyl content of 49.7 millimoles per 100 grams.The Wrinkle Recovery Tests (ASTM D1295- 60T) yielded respectively wetand dry values of 230 and 203, warp and filling, (W and F), as comparedto the 10% sodium hydroxide treated fabric values, which wererespectively 171 and 187 (W and F).

The fabric treated by process of this invention had a water ofimbibit-ion value of 50%, while the 20% sodium hydroxide treated fabrichad a value of 37%, and the untreated printcloth a value of 31%.

Note: The water of imbibition. value is here used as the criterion forevaluation of the absorbency of the fabrics, and is substantiallydifferent from moisture regain at 65% relative humidity. (Ref. TextileResearch 1., vol. 30, No. 3, March 1960.)

Example 2 A sample of cotton printcloth was padded with a solutioncontaining parts by Weight of the sodium salt of beta-chloroacrylicacid, 20 parts by weight of sodium hydroxide, and 70 parts by weight ofwater. The wet sample was framed, dried and cured, washed, and dried aswas the sample processed in Example 1.

The product was insoluble in the 0.5 molar cupriethylenediaminehydroxide solution, and had a carboxyl content of 38.7 millimoles per100 grams. The wet and dry wrinkle recovery angle values wererespectively 216 and 181 (W and F) compared with the correspondingvalues of 171 and 187 [for the 20% sodium hydroxide treated fabricvalues.

The fabric treated by the process of our invention had a water ofirnbibition value of 44%, while the 20% sodium hydroxide treated fabrichad a value of 37%, and the untreated cotton printcloth a value of 31%.

Example 3 A sample of cotton printcloth was padded with a solutioncontaining 10 parts by weight of the sodium salt ofalpha-beta-dichloroacrylic acid, 20 parts by weight of sodium hydroxide,and 70 parts by weight of water. The wet sample was framed, dried andcured, washed, and dried as was the sample processed in Example 1.

.The product was insoluble in the 0.5 mole cupriethylenediaminehydroxide solution, and had a carboxyl content of 32.5 millimoles per100 grams. The wet and dry wrinkle recovery angle values wererespectively 227 and 198 (W and F) compared with the corresponding 171and 187 values of the 20% sodium hydroxide treated fabric.

Example 4 A sample of cotton printcloth was padded with a solutioncontaining 10 parts by weight of alpha-beta-dichloroacrylic acid, and 90parts by weight of water, and dried in a vented oven for minutes at 65C. The dry fabric sample was then padded with a sodium hydroxidesolution, placed on a pinframe, and cured 15 minutes at 120 C. Thechemically modified fabric was then washed with water until free ofcaustic, and dried. It was insoluble in the 0.5 molarcupriethylenediamine hydroxide solution, and had a carboxyl content of19 millimq s P 100 m 4 Example 5 A sample of cotton printcloth waspadded with a solution containing 10 parts by weight ofalpha-beta-dichloroacrylic acid, and parts by weight of water, and driedin a vented oven for 15 minutes at 65 C. The dry fabric sample was thenpadded with a 40% sodium hydroxide solution, placed on a pinframe, andcured 30 minutes at 105 C. The chemically modified fabric was removedfrom the frame, washed free of caustic, refrained, and dried. It wasinsoluble in the 0.5 molar cupriethylenediamine hydroxide solution, andhad a carboxyl content of 23 millimoles per grams.

We claim:

1. A process for crosslinking cellulose which comprises:

(a) impregnating the said cellulose with an aqueous mixture containingan alkali salt of a halo-acrylic acid selected from the group consistingof the potassium salt of alpha-chloroacrylic acid, the sodium salt ofbeta-chloroacrylic acid, and the sodium salt of alphabeta-dichloroacrylic acid in combination with sodium hydroxide, theratio of salt to sodium hydroxide to water being 1:2:7, respectively,and

(b) drying and curing the said impregnated cellulose for about from 10to 30 minutes, at about from 100 to 120 C., the shorter periods of timeused with the higher temperatures.

2. The process of claim 1 wherein the said alkali salt is the potassiumsalt of alpha-chloroacrylic acid.

3. The process of claim 1 wherein the said alkali salt is the sodiumsalt of beta-chloroacrylic acid.

4. The process of claim 1 wherein the said alkali salt is the sodiumsalt of alpha-beta-dichloroacrylic acid.

5. A process for crosslinking cellulose which comprises:

(a) impregnating the said cellulose with an aqueousalpha-beta-dichloroacrylic acid solution,

( b) drying the wet cellulose for about 15 minutes at about 65 C.,

(c) impregnating the dried cellulose with an aqueous sodium hydroxidesolution about from 20% to 40% by Weight, and

(d) drying and curing the Wet cellulose for about from 15 to 30 minutes,at about from to C., the shorter periods of time used with the highertemperatures.

References Cited by the Examiner UNITED STATES PATENTS 2,524,399 10/1950 Schoene et al. 8-116 3,208,994 9/1965 Flodin 260-209 DONALD E.CZAJA, Primary Examiner.

R- W. MULCAHY, Assistant Examiner.

1. A PROCESS FOR CROSSLINKING CELLULOSE WHICH COMPRISES: (A)IMPREGNATING THE SAID CELLULOSE WITH AN AQUEOUS MIXTURE CONTAINING ANALKALI SALT OF A HALO-ACRYLIC ACID SELECTED FROM THE GROUP CONSISTING OFTHE POTASSIUM SALT OF ALPHA-CHLOROACRYLIC ACID, THE SODIUM SALT OFBETA-CHLOROCACRYLIC ACID, AND THE SODIUM SALT OFALPHA-BETA-DICLOROACRYLIC ACID IN COMBINATION WITH SODIUM HYDROXIDE, THERATIO OF SALT TO SODIUM HYDROXIDE TO WATER BEING 1:2:7. RESPECTIVELY,AND (B) DRYING AND CURING THE SAID IMPREGNATED CELLULOSE FOR ABOUT FROM10 TO 30 MINUTES, AT ABOUT FROM 100* TO 120*C., THE SHORTER PERIODS OFTIME USED WITH THE HIGHER TEMPERATURES.